Leaderboard

Can you move another 400mm away from your neighbour?! That would simplify things greatly.

Mid sections of pipe runs not haunched? To prevent deflection. Foreign objects like a 1/3 of a patio slab or a house brick, visible when migrating the spoil and back-filling.

You make a good point about the skills you have, I accept that. The regs have become a lot more stringent particularly in relation to portal frames on or near boundaries. Best thing you can do is to give your SE a call and discuss.

Google says.. Minimum Dimensions: Both the clear opening width and height must be at least 450mm. Total Area: The clear openable area must be at least 0.33m^2. If you make the opening width the minimum 450mm, the height must be at least 735mm to 750mm to hit the area required. Height: The bottom of the openable area should be no more than 1,100mm (1.1m) above the internal floor level for safe access.